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VV'JI. BURNET, OF NEW YORK, N. Y.

SLATE-PENCIL SHARPENER.

Specification of Letters Patent No. 21,649, dated October 5, 1858.

T0 all whom it may concern.'

Be it known that I, VILLIAM BUnNn'r, of the city and State of N ew York, have made certain new and useful Improvements in the article called Pencil-Sharpeners and used for shaping and pointing slate-pencils, whereby increased excellence and durability of the instrument and greater' economy in the cost of manufacture are attained; and to give others skilled a knowledge of my improvement I give the following description, illustrated by the accompanying drawings, forming a part of my specifications, reference being made in them and to the letters of indication marked thereon, showing the several parts.

Descripton 0] dmwz'ags.-Figure l represents the instrument when complete. A, A, are two round wires of steel with a well defined and sharp screw thread cut thereon. B, is a plate of any suitable sheet metal as iron, brass or tin plate, to which these threaded wires are attached; the plate also being the means of fastening the instrument to the frame of the slate when it is desirable. The threaded wires are placed relatively to each other in an acute angular position so that all portions of the pencil point may be reached by the teeth or threads of the wires.

Fig. 2 shows the parts detached; A, A, the wires, slightly pointed on the ends; B the plate of metal with its two ends turned up at right angles which ends after t-he wires are placed in proper position are turned over confining them in their places.

To use the instrument it is merely necessary to run the pencil longitudinally upon the bars when by this process a sufliciently sharp point is obtained. The larger point of the pencil may be cut to any desirable taper by rubbing it only where the bars are somewhat separated; in this way the point is not touched. These wires are from 1/12 to l/lG inch diameter, and from one to three inches long, though I have found in practice that one and one half inch is sufficiently long for all practical purposes.

I am aware that instruments have before been made for sharpening slate pencils, as

plane and hollow tiles. Therefore I do not claim to be the first inventor of a slate pencil Sharpener, but all the instruments with which I am acquainted have no means of renewing the cutting surfaces after they are worn-except by recutting them, while in mine it is merely necessary to turn the rods a little in the plate and a new cutting surface is brought into action. Again there is no method of making perfectly regular cutting surfaces with such facility as by the process I have described. I do not confine myself to the exactanethod of cutting teeth upon these wires, as it is evident that a toothed cutter may be used, and the teeth chased upon the wires in the turning lathe. Neither do I confine myself tothe exact method of fastening the wires upon the plate, as it is obvious that various means may be used to effect the same. But in the above description I have set forth the way which in practice I have found the simplest and mostfeconomical for producing the instruments.

My claim therefore is- To the manufacture of a pencil Sharpener, made of inclined cylindrical rods, having raised teeth upon them, either in the form of screw threads, or sharp parallel ridges; and the attachment of these to any suitable plate or frame work of metal for securing the cylindrical bars or rods in their proper position and for securing the whole tothe frame work of the slate-made and arranged substantially as described in the foregoing specification.

IVILLIAM BURNET.

Vitnesses HALSTED C. BURNET, THOMAS F. CALLAHAN. 

